Particulate mercury is one of the most abundant mercury species to which microbial methylators are exposed. Previous studies have shown that nanoparticulate mercury (Hg-NPs) is a potential source of bioavailable mercury for methylation in soils. However, the particle concentration and size of indigenous Hg-NPs in complex soil matrices are largely unknown, which hamper reliable risk assessments of Hg-NPs in environmental relevant scenarios.
In a new study published in Environmental Science & Technology, a research group led by Professor Yujun Wang from Institute of Soil Science, Chinese Academy of Sciences, demonstrates the experimental determinations of indigenous Hg-NPs in natural soils.
Coupled to single particle inductively coupled plasma-mass spectrometry (spICP-MS), the research team developed a standardized protocol for extraction and quantification of Hg-NPs in natural soils with different properties. High particle number-, particle mass-, and total mass-based recoveries were obtained for spiked HgS-NPs (74–120%). Researchers found that indigenous Hg-NPs across soils were within 107–1011 NPs g–1, corresponding to 3–40% of total Hg on a mass basis. Moreover, these indigenous Hg-NPs contributed to 5–65% of the measured methylmercury in soils. Metacinnabar was the primary Hg species in extracted soil samples from the Wanshan mercury mining site, as characterized by X-ray absorption spectroscopy and transmission electron microscopy. This work provides detailed information on Hg-NP number/mass concentrations and size, which will not only strengthen our understanding of mercury methylation processes governing the public exposure to MeHg but also guide further studies focusing on the biogeochemical cycling of Hg-NPs (https://doi.org/10.1021/acs.est.1c07039).
